This is super cool science fair project that I made as a personal project. This can be used as a security system where if you block the Laser, a buzzer will buzz.
1. One breadboard
4. 10k resistor
5. Piezzo buzzer
6. 9v battery
7. 9v battery holder
8. Hook up wires
9. Mirrors (optional)
11. laser light (any torch will also work if u don't use mirrors and poles and just want to build the circuit. A torch will be ideal if just want to show the concept of the circuit but u have to hold it closer)
Step 1: Circuit
Make the circuit on a bread board according to the circuit diagram shown.
Step 2: Connect the Batteries
Connect the batteries to the circuit board along with the LDR.
Step 3: Test Your Security System.
See that after connecting the batteries, the buzzer will start buzzing. Take a Laser pointer and aim it to the LDR. The buzzer will stop buzzing. If it doesn't, then check the circuit again and again.
Step 4: Using Mirrors (optional)
U can mount the circuit to a wooden pole and put some more wooden poles and mount mirrors on them and on the last pole u can mount the Laser pointer. Then u turn on the Laser and u can disconnect the batteries for now. After u turn on the Laser light, then position the mirrors so the reflect the laser in a zig zag way and make the Laser finally reflect to the LDR in the circuit. Connect the batteries. Now go through the way and prevent the Laser from being reflected. Then u hear the buzz! U can use smoke to make the Laser visible.